Several sulfamoyl substituted phenethylamine derivatives having strong α-adrenergic blocking activity are disclosed in U.S. Pat. No. 4,703,063. U.S. Pat. No. 4,731,478 discloses the (−) isomer of 5-[2-[2-(2-ethoxyphenoxy)ethylamino]-2-methylethyl]-2-methoxybenzene sulfonamide, that is, tamsulosin, having the following formula:

Tamsulosin is used in the treatment of benign prostatic hyperplasia (BPH), a condition characterized by enlargement of prostatic tissue, which results in obstruction of proximal urethra.
Tamsulosin primarily metabolizes to mainly five metabolites, one of which M4 of Formula I has been found to be almost equipotent to tamsulosin with respect to α1 adrenoreceptor binding (Taguchi et al., J. Pharmacol. Exp. Ther., 1997, 280 (1), 1–5). The authors specify that M4 was used in its racemic form. The optically-active single enantiomer of this metabolite could not be obtained viz., Xenobiotica, (1996), 26(3), 355–365; and Xenobiotica, (1996), 26(6), 637–645.

Enantiomers are structurally identical compounds, which differ only in that one isomer is a mirror image of the other and the mirror images cannot be superimposed. This phenomenon is known as chirality. Most biological molecules exist as enantiomers and exhibit chirality. Although structurally identical, enantiomers can have profoundly different effects in biological systems: one enantiomer may have a specific biological activity while the other enantiomer has no biological activity at all, or may have an entirely different form of biological activity.
Therefore, there is a need to develop a method for the preparation of optically active compound of Formula I in order to explore the potential of the compound as α1-adrenoceptor antagonist. Our attempts to obtain the desired compound directly from tamsulosin by selective O-demethylation of tamsulosin have been unsuccessful.